So what did you finally end up as your go to pellet for the f4? I just grabbed one from wally world and I'm going to order some pellets. Thx!
I bought a F4 over a year ago like the OP did. Once "broken-in," I found that H&N FTT's at 4.52mm sizing and also JSB heavies shot excellent through it. Mileage may vary depending on how your barrel is in yours. After 500 shots, the lockup on the barrel went to crap quickly and needed some TLC.
I have NPE/NP2's in .177 and .22, and the .22 is great, and far-less "pellet picky." The thing I like about the NP2's is that the build of the rifles is more solid, but the added velocity in .177 forces the use of slightly heavier pellets to keep velocities under the trans-sonic range to keep decent accuracy.
My .22 is a real shooter... but also keep in mind that I modified the trigger with a lighter spring, stoned the sear to a nice polish, put a new viton oring in the barrel breach face OTB, removed the screws and used blue Loctite all-around during re-assembly, went with different scope rings and better scopes, etc. I am doing the same with the .177 NP2 this week.
They are not perfect out of the box, but with some extra time, elbow-grease, and dedication (and money), they can be good shooters. If you hit their sales up on Crosman's website before January 1, you can pick up something even better and cheaper than the F4.
PT